The present invention relates to suspended ceiling systems and particularly to connection systems for interlocking the main runners and cross runners of such suspended ceiling systems.
The main runners and cross runners of suspended ceiling systems are typically comprised of a web portion with a panel supporting flange portion at its lower edge. The main runners are connected in end-to-end relationship to form parallel runs while the cross runners are connected perpendicularly between the main runners. Thus, the interconnected cross and main runners cooperate to form a grid system for supporting ceiling panels.
Interconnection of the cross runners with the main runners is usually accomplished by forming a tongue-shaped connector on the end of each cross runner, which is received by a slot in the web of the main runner. Various types of locking systems are provided to fasten the end connector to the main runner web or to the end connector of an opposed cross runner. One such interlocking system is disclosed in U.S. Pat. No. 4,108,563, issued to Brown et al.
It is desirable for aesthetic reasons to interconnect the cross and main runners so that their ceiling panel support flanges lie in the same plane. This may be accomplished by properly orienting the slots and end connectors so that the end connectors are supported by the slots at a level which permits the cross runner support flange to abutt the main runner support flange. However, this method of aligning the flanges is disadvantageous, since it requires that the positioning of the notch in the web, and the positioning of the connector on the cross runner, be within relatively exact tolerances to insure accurate alignment of the panel support flanges. The prior art has responded to this problem by extending the cross runner flange so that it overlaps or overrides the top of the main runner flange. Typically, the end of the cross runner flange is bent to form a jog, so that it is raised above the central plane of the flange by an amount equal to its thickness, as illustrated in U.S. Pat. No. 3,501,185, issued to Brown et al. This permits the main and cross runner flanges to lie in the same plane, except at the point of overlap, where the jogged overlapping portion of the cross runner flange lies above this plane. The jog, however, creates a raised portion which is equal in height to the thickness of the cross runner flange. This raised portion is disadvantageous, since it prevents the ceiling panels from lying flush against the flanges throughout their length. Moreover, it is impractical to reduce the height of this raised portion by making the cross runner flange very thin, since the flanges must have a reasonable degree of structural strength to provide proper support for the ceiling panels.
As with cross runners, interconnection of main runners is typically accomplished by providing interlocking end connectors. It is common in the prior art to provide a strap or loop which extends perpendicularly outward from the side of the end connector, as shown in U.S. Pat. No. 3,979,874, issued to Cubbler, Jr., et al. The loop receives the end connector of an adjacent main runner and holds the end connectors together, in side-by-side relationship, to prevent lateral separation. However, for manufacturing convenience, the loop is usually formed by lancing the side of its end connector, which creates an aperture. When the leading edge of the adjacent end connector is inserted through the loop, it may catch on the side of the aperture, thereby making assembly difficult.